Turbo Exhaust

[ausyota]

I have a second hand turbo kit I am fitting to my lux that has a TB25 turbo.
The dump pipe(I think thats what the pipe that comes out of the back of the turbo is called isnt it?) that came with it is only 2 1/4 inch pipe.
I was planning on putting a 2 1/2 inch exhaust on.
Is it worth getting a 2 1/2 dump pipe?
Do they reuse the flange and modify it to fit the bigger pipe or is it part of a new dump pipe?

Paul.

[toughnut]

The pipe imediately after the turbo on both the exhaust (dump pipe) and the intake make quite a big difference to the efficiency of the turbo. The bigger the pipe the quicker and easier the gases from the turbo can expand which means less back pressure on the turbo. What this does is it lets the turbo spin up quicker giving you more power for less work, which in turn means less heat in the engine. This allows you to run more fuel which gives you more power and torque.

[brad-chevlux]

I have a second hand turbo kit I am fitting to my lux that has a TB25 turbo.
The dump pipe(I think thats what the pipe that comes out of the back of the turbo is called isnt it?) that came with it is only 2 1/4 inch pipe.
I was planning on putting a 2 1/2 inch exhaust on.
Is it worth getting a 2 1/2 dump pipe?
Do they reuse the flange and modify it to fit the bigger pipe or is it part of a new dump pipe?

Paul.

personly i would be using a 3 inch for the whole thing.
most turbos have new flanges available for them.

as toughnut said pay carful attension to all the pipe work it will make a huge difference in the way the turbo comes on boost and the power/driveability you get from the setup.

don't be fooled into thinking keeping the pipe work the same size as the outlet of the turbo will help reduce turbo lag/ throttle lag.

and if it's simple to move other engine bay parts to get better pipe work do it

[ausyota]

personly i would be using a 3 inch for the whole thing.

3 inch would be cool but I think a little overkill for my little 4cyl lux.
The pipe would end up bigger than the flange that bolts onto the turbo:shock:
I think I will ring a turbo place tomorrow and see what they say and how much it is going to cost me.
Paul.

[toughnut]

The pipe would end up bigger than the flange that bolts onto the turbo:shock:

Thats exactly right. Thats pretty much the idea. Remember that the air is compressed when it goes through the turbo and ideally you want as little back pressure in the exhaust otherwise the turbo is not only working to push air into the motor but out as well which means it won't spin up as quick and will have to work harder to produce the same power, which in turn means more heat that can hurt your engine.

[brad-chevlux]

personly i would be using a 3 inch for the whole thing.

3 inch would be cool but I think a little overkill for my little 4cyl lux.
The pipe would end up bigger than the flange that bolts onto the turbo:shock:
I think I will ring a turbo place tomorrow and see what they say and how much it is going to cost me.
Paul.

I work at one those places. it's very common for the pipe work to be bigger then the outlet on the exhaust housing. this last week i have been doing a turbo upgrade, the turbo used has a 2.5inch exhaust outlet.
the first thing we did was weld a 2.5 to 3 inch adapter cone to it so we could use 3 inch pipe.

what you need to remember is that when you add boost to your engine you are effectivly making the engine bigger. every 14.7PSI doubles the capacity of the engine.

[optical]

i wouldnt run 1bar (14.7psi) into an engine not designed / tuned for turbo applications. you have tothink about intercooling, extra fueling, timing etc.

or did i just read that post wrong ?

[fisho64]

dont bother with 3" exhaust, waste of money for the hilux. Even mandril bent is more for those that have too much money. Its like the difference between steel and alloy wheels, they look great and probably make a SMALL difference, but you wouldnt notice if you didnt know the difference.
Also, the the turbo outlet is smaller for a reason, to increase the velocity of the gas thru the turbo. As the gas travels thru the exhaust and cools it will expand a bit.

[Bush65]

snip
As the gas travels thru the exhaust and cools it will expand a bit.

That statement could be missleading.

Yes the gas will expand in the exhaust. Because the pressure drops.

Yes it will cool. Because of heat transfer.

But it wont expand because it cools.

A larger exhaust will reduce the back pressure and lower back pressure allows the turbo to perform better.

[uninformed]

i have a 3 inch mandrel bent system on my 2.5ltr tdi landrover. it made a big difference over the 2 1/2 factory system. flat out with my trailer on was 108km/h now about 130km/h and the turbo spools quicker meaning i'm not changing down all the time. it runs 17psi of boost
cheers,serg

[toughnut]

dont bother with 3" exhaust, waste of money for the hilux. Even mandril bent is more for those that have too much money. Its like the difference between steel and alloy wheels, they look great and probably make a SMALL difference, but you wouldnt notice if you didnt know the difference.
Also, the the turbo outlet is smaller for a reason, to increase the velocity of the gas thru the turbo. As the gas travels thru the exhaust and cools it will expand a bit.

You obviously haven't had access to a dyno and had the opportuninty to test both types of exhaust. This is my intake pipe from my turbo but the same principal applies to the exhaust. First pipe was skinny and longer to get around obstacles in the engine bay without tight turns.


Now just by changing the pipe to a larger diameter straight out of the turbo I gained an extra 5kw without doing anything else. On top of this the turbo came onto full boost earlier and held full boost longer.

[more power]

so for the dum question what is the alloy thing on top of the motor...
is that a water to air intercooler...

[Shadow]

wtf is that tank?

water/air intercooler?

[fisho64]

bush I didnt say it will cool because it expands.
The standard exhaust is about 2 1/4". 2 1/2" with a good straight thru muffler is sufficient. Unless you'v got too much money the 3" at probably double cost isnt worth it, especially not mandrel bent.
I SERIOUSLY wouldnt recommend running a 2.8 at 17 psi boost and doubly so if not intercooled.

[fisho64]

Is that an intercooler on there? Hooked into the heater lines/engine coolant? If so I think you would get more benefit by running the intercooler with its own supply and small radiator as your intercooler is pumping water thru it at probably 70 degrees plus and (depending on boost) the air it is trying to cool is only maybe 10 or 20 degrees higher than that? It can be done with a car heater core and little electric pump easily.

[spazbot]

i thin k that was his inital setup and now has a small rad and thermo fan on the tray for it

[chips59]

Call me dumb, but are you gise saying if you weld a flange on the back of the turbo which is either 21/2 or21/4 up to 3inch and continue through with high flow muffler this will make a big differance to the power and the spooling up?

[toughnut]

You weld a cone shaped piece of tube adaptor that allows you to run 3" piping. You can see what we are talking about on my piping just below the red silicone and yes it does make a difference to the power that the turbo adds to the motor. What it does is lessen the pressure after the turbo so that the turbo doesn't have to push as hard to send the gases down the exhaust. This in turn lets the turbo spin up easier which means that it will produce the same power for less effort. It has a follow on effect where the exhaust gas temperature will be lower allowing you to put more fuel into the motor giving you more power.

[chips59]

thank for reply toughnut. So you do this on both sides of the turbo? Intake and exhaust

[toughnut]

Yeah if you can. I didn't think it would make much difference until I had access to as much dyno time as I needed. 5kw may not seem like much but it changed the whole characteristic of the vehicle. It drives much better than before and stays on power right up to red line. Much more drivable.

[brad-chevlux]

dont bother with 3" exhaust, waste of money for the hilux. Even mandril bent is more for those that have too much money. Its like the difference between steel and alloy wheels, they look great and probably make a SMALL difference, but you wouldnt notice if you didnt know the difference.
Also, the the turbo outlet is smaller for a reason, to increase the velocity of the gas thru the turbo. As the gas travels thru the exhaust and cools it will expand a bit.

why dont you give john from Townsville turbo suplies a call, over 20 years in the business and a reputation across the country for being one of the best counts for some thing.

it was on his advice to use the adapter and 3 inch pipe on a turbo with a 2.5 inch outlet.

he has also shown on a number of turbos (using a test bed) that the dump pipe is one the mayjor factors in how the turbo performs.

one turbo even showed up a 50HP increase in flow just by going from 3inch to 3.5inch dump, while still using the same 3inch exhaust system.

i wouldnt run 1bar (14.7psi) into an engine not designed / tuned for turbo applications. you have tothink about intercooling, extra fueling, timing etc.

or did i just read that post wrong ?

i think you just read my post my post wrong.

it was only to show what happens and using the 14.7psi was only to make it simple as that double atmo pressure and therefor doubles the air intake.

i would also assume that any one fitting a turbo would take the wiser path and fit some sort of intercooling and have the engine properly tuned

[Dzltec]

Hi Toughnut, got any dyno sheets to show us just how good your beast is with that intercooler??

[toughnut]

Things are a bit tight cash wise at the moment but I'll be jumping back on the dyno very soon cause I want to see what effect it's had as well.

[fisho64]

[
one turbo even showed up a 50HP increase in flow just by going from 3inch to 3.5inch dump, while still using the same 3inch exhaust system.

bet it wasnt a 2.8 hilux!!

[ausyota]

I rang a turbo place yesterday and they said they had nothing "off the shelf" but said just to go see an exhaust place amd get them to cut the pipe off and fit a cone up to the bigger size.
I questioned the point of that with him having the exhaust resticted by the 2 1/4 outlet then going into 3" pipe and he said it shouldnt matter because the turbo wheel is only 2 inch anyway.
Is it worth getting the dump pipe flange machined to fit the bigger pipe? It can probably be taken up to 2 1/2 easily enough but I will still have to cone it up to fit 3".
Paul.

[toughnut]

You don't need to machine the turbo housing. Just fit the bigger dump pipe.

[MKPatrolGuy]

Is the hole in the flange that bolts to the turbo any smaller than the outlet on the turbo itself? If it is smaller I would open it up to the size of the turbo outlet.

[toughnut]

Is the hole in the flange that bolts to the turbo any smaller than the outlet on the turbo itself? If it is smaller I would open it up to the size of the turbo outlet.

Yeah thats right. You'd get a flange to suit the turbo outlet but there is no need to enlarge the turbo housing itself.

[brad-chevlux]

[
one turbo even showed up a 50HP increase in flow just by going from 3inch to 3.5inch dump, while still using the same 3inch exhaust system.

bet it wasnt a 2.8 hilux!!

no, your right, a flow bench is not a 2.8L hilux.

but it does show the difference in flow between the two pipes

[fisho64]

Turbos dont produce horsepower, they contribute to an engines ability to produce it. (or increase its efficiency in the case of a diesel) It cannot be quantified without knowing what is attached to etc. A statement like that is overly simplistic.
Beware of what you are told by someone who is selling you something.